Respiratory Face Mask

Air pollution and climate change are two complex environmental problems that both related to large consumption of fossil fuels. One of the major airborne pollutants, particulate matter (PM), has raised serious concerns in recent years. PM is categorized by the particle size as PM2.5 andPM10. PM2.5 with small particle sizes can penetrate bronchi and lungs and poses a severe health threat to the public. To filter airborne pollutants, face masks have been widely used as safety equipment. Commercial face masks are usually made of many layers of fibers (μm-size in diameter) and capture PM particles by a combination of physical barriers and adhesion. To achieve a high PM removal efficiency, these face masks need to be thick and hence are often bulky and resistant to air flow (featured by a large pressure drop ΔP across the face mask). Consequently, breathing through these face masks can be uncomfortable or even dangerous for elderly people and people with lung diseases. Nanofibers with large surface area to volume ratio have shown great potential in filtration applications, including air filtration, dust capture as well as absorbing and detoxifying biological and chemical contaminants. Polymer nanofibers with polar functional groups such as polyacrylonitrile, polyimide, and polyamide have strong affinity to PM pollutants and therefore show high removal efficiency at low pressure drop and high optical transparency. These nanofibers are promising for use in face masks to achieve both high PM capture efficiency and sufficient air permeability [1, 2].

The following image shows how different layers are oriented to make a respiratory face mask. The nonwoven layer coated by nanofibers is located at the center and two other nonwoven layers are placed on both sides of the nonwoven with nanofiber coating to prevent damaging the nanofiber layer during production process or at the time of using.

According to BS EN 149:2001 standard for “filtering half masks” (also called filtering face pieces), FNM Co. Ltd., can produce different classes of respiratory face masks (FFP1, FFP2 and FFP3). The performance of FNM’s nanofiber-based respiratory face masks is compared with conventional masks (without nanofiber layer) in Table 1 and Figure 2.

References
1. Yang, Ankun, Lili Cai, Rufan Zhang, Jiangyan Wang, Po-Chun Hsu, Hongxia Wang, Guangmin Zhou, Jinwei Xu, and Yi Cui. "Thermal management in nanofiber-based face mask." Nano letters 17, no. 6 (2017): 3506-3510.
2. Akduman, C., and EP Akçakoca Kumbasar. "Nanofibers in face masks and respirators to provide better protection." In IOP Conference Series: Materials Science and Engineering, vol. 460, no. 1, p. 012013. IOP Publishing, 2018.